GENETICS: Our Family Tree

It’s all Relative! --Did you know we share 99.9% of our genes with other humans? --95% of our genes with chimpanzees? --92% of our genes with a mouse? --So was Dr. Seuss thinking about genetics?

It’s all in the genes! Genes -- the unit of heredity --carry the information about our traits --found in the chromosomes --pass trait information from parent to offspring

Combination Platter Egg + Sperm = Y U --You inherited 23 chromosomes from each parent. --Each of those chromosomes contained ALLELES. --Allele = different form of same gene. --The combination of those alleles = Y U!

Who’s the daddy? --Genetics is the study of heredity. --Gregor Mendel is the father of genetics. --He was a priest in a monastery who enjoyed gardening. --He was interested in the different characteristics of pea plants (yuck  ).

The Birds and the Peas --Mendel cross-pollinated 2 purebred pea plants. --He took the pollen from one plant and fertilized it with the other plant. --WHY? To see what he could see – the characteristics of the offspring!

Mendel’s Peas --Mendel noticed the size of pea plants varied. --He wondered what would happen if he crossed purebred plants? --Purebred – Tall or Short (no in betweens—ex. mediums)

Mendel’s cross between tall pea plants yielded all tall pea plants. His cross between small pea plants yielded all small pea plants. Tall x Tall = TallSmall x Small = Small X X== PP PPF 1

Mendel’s cross of tall plants with small plants resulted in tall plants. X = F 1 PP

Mendel then crossed the first generation (F 1 ) tall plants and the results (F 2 ) were 1 out of 4 Small. X = F1F1 F 2 F 2 Second Generation

Mendelalian Genetics --What did Mendel learn from his experiments? 1)Alleles are different forms of a gene. 2)Alleles are either DOMINANT or Recessive. 3)Phenotype = physical characteristic shown is a result of at least 2 alleles.

Mendelian Genetics -- DOMINANT allele is the trait that ALWAYS shows up in the Phenotype. -- DOMINANT allele is ALWAYS represented by a CAPITAL letter (T= Tall) -- GENOTYPE = combination of alleles --Purebred Tall Pea Plants have GENOTYPE TT -- TT = HOMOZYGOUS DOMINANT -- HOMOZYGOUS = SAME --Both alleles inherited are DOMINANT or the same

Mendelian Genetics -- Recessive alleles are weak and hidden by dominant allele. -- Recessive alleles DO NOT show up in Phenotype UNLESS two are together*. -- Recessive alleles are represented by a lower case letter --Purebred short pea plants have GENOTYPE tt -- tt is HOMOZYGOUS Recessive. --Both alleles are Recessive or the same.

Mendelian Genetics So what was the GENOTYPE of the first generation Tall plants from Slide 9? Tall x Small = Tall Tt = HETEROZYGOUS Dominant -- HETEROZYGOUS = two alleles are NOT the same --One allele is DOMINANT the other Recessive -- HETERO = different -- Phenotype = DOMINANT trait ALWAYS shows up --Plants are tall.

Say What?

Do you know …. Gregor Mendel Heredity Trait Genes Cross Pollination Alleles GENOTYPE Phenotype Purebred HOMOZYGOUS HETEROZYGOUS DOMINANT Recessive How to write the GENOTYPES ? P generation F 1 generation F 2 generation

To be continued... Punnett Squares, Codominance, Probability, and Blood Typing.. OH MY!!!!